altos/scheme: Avoid crashing with non-list in length

Use ao_scheme_cons_cdr to fetch the next list element as that returns
NULL for non-cons elements.

Signed-off-by: Keith Packard <keithp@keithp.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/src/scheme/ao_scheme_cons.c b/src/scheme/ao_scheme_cons.c
index 03dad956..21ee10cc 100644
--- a/src/scheme/ao_scheme_cons.c
+++ b/src/scheme/ao_scheme_cons.c
@@ -195,7 +195,7 @@ ao_scheme_cons_length(struct ao_scheme_cons *cons)
 	int	len = 0;
 	while (cons) {
 		len++;
-		cons = ao_scheme_poly_cons(cons->cdr);
+		cons = ao_scheme_cons_cdr(cons);
 	}
 	return len;
 }